Diagnosing method and diagnosing device for abnormal cable connection of incremental encoder

A diagnosing method for an abnormal cable connection of an incremental encoder includes: receiving a first-set of differential signals including one of signals A/Ā and one of signals B/B and a second-set of differential signals including one of signals A/Ā and one of signals B/B from the incremental encoder by two encoder modules; calculating a first signal-information group and a second signal-information group according to the first-set and second-set of differential signals; calculating a first parameter-information group and a second parameter-information group based on the first and second signal-information groups; determining whether a first signal direction is consistent with a second signal direction according to the first and second parameter-information groups; calculating a position-feedback control parameter for a motor according to a signal-information group corresponding to a normal set of differential signals when the first signal direction is determined to be inconsistent with the second signal direction.